JP2013534075A - Method and apparatus for receiving data from a base station in a relay node of a wireless communication system - Google Patents

Abstract

A method for a relay node to receive a relay node specific downlink physical shared channel from a base station in a wireless communication system.
The present invention demodulates a relay node specific downlink physical control channel using a relay node specific reference signal, and specific downlink control information is detected from the demodulated relay node specific downlink physical control channel. The relay node specific downlink physical shared channel is demodulated under the assumption that the relay node specific downlink physical shared channel is transmitted through a single antenna port with a predetermined antenna port and scramble identifier, including. Here, the specific downlink control information indicates a fallback mode, and the predetermined antenna port and scramble identifier are an antenna port 7 and a scramble identifier 0, respectively.
[Selection] Figure 9

Description

  The present invention relates to a radio communication system, and more particularly to a method for receiving data from a base station in a relay node of the radio communication system and an apparatus therefor.

  As an example of a wireless communication system to which the present invention can be applied, a third generation partnership project (3GPP) long-term evolution system (hereinafter referred to as “LTE”) will be schematically described.

  FIG. 1 is a diagram schematically showing an evolved universal mobile communication system (E-UMTS) network structure as an example of a wireless communication system. E-UMTS is a system evolved from the existing general-purpose mobile communication system (UMTS), and basic standardization work is currently underway in 3GPP. In general, E-UMTS can also be referred to as an LTE system. Refer to Release 7 and Release 8 of “3rd Generation Partnership Project; Technical Specification Group Radio Access Network” for the detailed contents of the technical standards of UMTS and E-UMTS, respectively.

  Referring to FIG. 1, E-UMTS is a connection gateway that is located at the end of a terminal (UE) 120, base stations (evolution Node B, eNB) 110a and 110b, and a network (E-UTRAN) and connects to an external network. (AG) is included. The base station can transmit multiple data streams simultaneously for broadcast service, multicast service and / or unicast service.

  One base station has one or more cells. The cell is set to any one of bandwidths such as 1.25, 2.5, 5, 10, 15, and 20 MHz, and provides a downlink or uplink transmission service to a large number of terminals. Separate cells can be configured to provide separate bandwidth. The base station controls data transmission / reception to a large number of terminals. For downlink (DL) data, the base station transmits downlink schedule information, time / frequency domain in which data is transmitted to the corresponding terminal, encoding, data size, hybrid automatic repeat request (HARQ) related information, etc. To inform. Also, for uplink (UL) data, the base station transmits uplink schedule information to the corresponding terminal, and informs the time / frequency domain, coding, data size, HARQ related information, etc. that can be used by the corresponding terminal. . An interface for transmitting user information or control information can be used between the base stations. The core network (CN) can be composed of an AG, a network node for user registration of a terminal, and the like. AG manages the mobility of a terminal for each location registration area (Tracking Area, TA) composed of a plurality of cells.

  Wireless communication technology has been developed up to LTE based on wideband code division multiple access (WCDMA), but the demands and expectations of users and operators are increasing. In addition, since other wireless connection technologies have been developed one after another, new technology evolution is necessary to be competitive in the future. There is a need for lower cost per bit, increased service availability, flexible frequency band usage, simple structure and open interface, and proper power consumption of terminals.

  In view of the above points, a method for receiving data from a base station by a relay node in a wireless communication system and an apparatus therefor are proposed below.

  A method for a relay node to receive a relay node specific downlink physical shared channel (R-PDSCH) from a base station in a multi-antenna wireless communication system according to an aspect of the present invention includes a relay node specific downlink physical control channel (R- PDCCH) is demodulated using a relay node specific reference signal, and when specific downlink control information is detected from the demodulated relay node specific downlink physical control channel, the relay node specific downlink physical shared channel is predetermined. And demodulating a relay node specific downlink physical shared channel under the assumption that it was transmitted through a single antenna port using a plurality of antenna ports and scrambled identifiers.

  On the other hand, the relay node in the wireless communication system, which is another aspect of the present invention, transmits a relay node specific downlink physical control channel (R-PDCCH) and a relay node specific downlink physical shared channel (R-PDSCH) from the base station. A receiving module for receiving and demodulating a relay node specific downlink physical control channel based on a relay node specific reference signal, and based on specific downlink control information detected from the demodulated relay node specific downlink physical control channel A processor that decodes the relay node specific downlink physical shared channel, the processor assuming that the relay node specific downlink physical shared channel was transmitted through a single antenna port using a predetermined antenna port and a scramble identifier Under Characterized by demodulating the relay node specific downlink physical shared channel.

  Here, the relay node specific reference signal is a demodulation reference signal (DM-RS), the specific downlink control information is downlink control information indicating the fallback mode, and the down indicating the fallback mode. The link control information is characterized by a downlink control information (DCI) format 1A.

  Preferably, the predetermined antenna port and scramble identifier may be the antenna port and scramble identifier of the relay node specific reference signal used when demodulating the relay node specific downlink physical control channel, and the predetermined antenna port and scramble identifier is These may be antenna port 7 and scramble identifier 0, respectively.

  According to the embodiment of the present invention, in a wireless communication system, a relay node can effectively receive data from a base station.

  The effects obtained by the present invention are not limited to the effects mentioned above, and other effects that are not mentioned will be apparent to those having ordinary knowledge in the technical field to which the present invention belongs from the following description. Will be understood.

1 is a diagram schematically showing an E-UMTS network structure as an example of a wireless communication system. FIG. It is a figure which shows the structure of the control plane and user plane of a radio | wireless interface protocol between the terminal based on 3GPP radio | wireless connection network specification, and E-UTRAN. It is a figure for demonstrating the general signal transmission method using the physical channel and these channels which are used for 3GPP system. It is a figure which illustrates the structure of the radio | wireless frame used with a LTE system. It is a figure which illustrates the structure of the downlink radio frame used with a LTE system. It is a block diagram of a general multiple antenna (MIMO) communication system. It is a figure which shows the structure of the reference signal in the LTE system which supports the downlink transmission which uses four antennas. It is a figure which shows the relationship between the transmission mode for transmitting PDSCH, and the DCI format instruct | indicated by PDCCH. It is a figure which shows the structure of a relay backhaul link and a relay access link in a radio | wireless communications system. It is a figure which illustrates relay node resource division. It is a figure which shows the case where 12 resource elements for DM-RS are allocated in one resource block pair. It is a figure which shows the case where 24 resource elements for DM-RS are allocated in one resource block pair. It is a block block diagram of the communication apparatus which concerns on one Example of this invention.

  The structure, operation, and other features of the present invention can be easily understood from the embodiments of the present invention described below with reference to the accompanying drawings. In the embodiment described below, the technical features of the present invention are applied to a 3GPP system.

  In the present specification, an embodiment of the present invention will be described using an LTE system and an advanced LTE (LTE-A) system, but this is only an example, and the embodiment of the present invention may be applied to any of the above definitions. It may be applied to a communication system. In addition, although the present specification describes an embodiment of the present invention based on a frequency division duplex communication (FDD) system, this is exemplary, and the embodiment of the present invention is divided into frequency division halves. The present invention can be easily modified and applied to the heavy communication (H-FDD) system or the time division duplex communication (TDD) system.

  FIG. 2 is a diagram illustrating a structure of a control plane and a user plane of a radio interface protocol between a terminal and E-UTRAN based on the 3GPP radio access network standard. The control plane means a path through which a control message used by a terminal (UE) and a network to manage a call is transmitted. The user plane means a path through which data generated in the application layer, for example, voice data or Internet packet data is transmitted.

  The physical layer, which is the first layer, provides an information transfer service (Information Transfer Service) to an upper layer using a physical channel. The physical layer is connected to an upper medium access control layer through a transmission channel. Data moves between the medium connection control layer and the physical layer through the transmission channel. Data moves between the physical layer on the transmission side and the physical layer on the reception side through a physical channel. The physical channel uses time and frequency as radio resources. In particular, the physical channel is modulated on the downlink with an orthogonal frequency division multiple access (OFDMA) scheme and on the uplink with a single carrier frequency division multiple access (SC-FDMA) scheme.

  The medium connection control (MAC) layer in the second layer provides services to a radio link control (RLC) layer, which is an upper layer, through a logical channel. The second layer RLC layer supports reliable data transmission. The functions of the RLC layer may be implemented by function blocks inside the MAC. The packet data fusion protocol (PDCP) layer in the second layer has a header compression function that reduces unnecessary control information in order to efficiently transmit IP packets such as IPv4 or IPv6 over a low bandwidth wireless interface. Run.

  The radio resource control (RRC) layer located at the bottom of the third layer is defined only in the control plane. The RRC layer is responsible for controlling logical channels, transmission channels, and physical channels in association with radio bearer (RB) setup, reconfiguration, and release. RB means a service provided by the second layer for data transmission between the terminal and the network. For this purpose, the RRC layer of the terminal and the network exchanges RRC messages. If there is an RRC connection between the terminal and the RRC layer of the network, the terminal is in the RRC connected state (Connected Mode), otherwise it is in the RRC dormant state (Idle Mode). The non-connection layer (NAS) layer above the RRC layer is responsible for functions such as session management and mobility management.

  One cell constituting a base station (eNB) is set to any one of bandwidths such as 1.25, 2.5, 5, 10, 15, 20 MHz, and downlink or uplink to a plurality of terminals Provide transmission service. Separate cells can be configured to provide separate bandwidth.

  The downlink transmission channel for transmitting data from the network to the terminal includes a broadcast channel (BCH) for transmitting system information, a call channel (PCH) for transmitting call messages, and a downlink shared channel (SCH) for transmitting user information or control messages. There is. The information or control message of the downlink multicast or broadcast service may be transmitted through the downlink SCH or may be transmitted through another downlink multicast channel (MCH). On the other hand, the uplink transmission channel for transmitting data from the terminal to the network includes a random access channel (RACH) for transmitting an initial control message and an uplink SCH for transmitting user information or a control message. The logical channels that are higher in the transmission channel and mapped to the transmission channel include broadcast control channel (BCCH), paging control channel (PCCH), common control channel (CCCH), multicast control channel (MCCH), multicast information channel ( MTCH).

  FIG. 3 is a diagram for explaining a physical channel used in the 3GPP system and a general signal transmission method using these channels.

  When the terminal is turned on or newly enters the cell, the terminal performs initial cell search work such as synchronization with the base station (S301). Therefore, the terminal can receive the primary synchronization channel (P-SCH) and the secondary synchronization channel (S-SCH) from the base station, synchronize with the base station, and acquire information such as the cell ID. Thereafter, the terminal can receive the physical broadcast channel from the base station and acquire the broadcast information in the cell. Meanwhile, the UE can check the downlink channel state by receiving a DL reference signal (DLRS) in the initial cell search stage.

  The terminal that has completed the initial cell search obtains more specific system information by receiving the physical downlink control channel (PDCCH) and the physical downlink shared channel (PDSCH) based on the information carried on the PDCCH. (S302).

  On the other hand, when the terminal is first connected to the base station or there is no radio resource for signal transmission, the terminal can perform a random access procedure (RACH) to the base station (steps S303 to S306). . Therefore, the terminal transmits a specific sequence as a preamble through a physical random access channel (PRACH) (S303 and S305), and can receive a response message for the preamble through the PDCCH and the corresponding PDSCH (S304 and S306). In case of contention based RACH, a collision resolution procedure can be further performed.

  The terminal that has performed the above procedure thereafter performs PDCCH / PDSCH reception (S307) and physical uplink shared channel (PUSCH) / physical uplink control channel (PUCCH) as a general uplink / downlink signal transmission procedure. ) Transmission (S308) can be performed. In particular, the terminal receives downlink control information (DCI) through the PDCCH. Here, the DCI includes control information such as resource allocation information for the terminal, and has different formats depending on the purpose of use.

  Meanwhile, the control information transmitted from the terminal to the base station through the uplink or received from the base station by the terminal includes a downlink / uplink acknowledgment / negative acknowledgment (ACK / NACK) signal, a channel quality indicator (CQI), Precoding matrix index (PMI), rank indicator (RI), etc. are included. In the 3GPP LTE system, a terminal can transmit control information such as the above-mentioned CQI / PMI / RI through PUSCH and / or PUCCH.

  FIG. 4 is a diagram illustrating a structure of a radio frame used in the LTE system.

Referring to FIG. 4, the radio frame has a length of 10 ms (327200 · T _s ) and is composed of ten equally sized subframes. Each subframe has a length of 1 ms and is composed of two slots. Each slot has a length of 0.5 ms (15360 · T _s ). Here, T _s represents a sampling time and is represented by T _s = 1 / (15 kHz × 2048) = 3.2552 × 10 ⁻⁸ (about 33 ns). A slot includes a plurality of OFDM symbols in the time domain and includes a plurality of resource blocks (RBs) in the frequency domain. In the LTE system, one resource block includes 12 subcarriers × 7 (6) OFDM symbols. A transmission time interval (TTI), which is a unit time during which data is transmitted, can be determined in units of one or more subframes. The structure of the radio frame described above is merely an example, and the number of subframes included in the radio frame, the number of slots included in the subframe, and the number of OFDM symbols included in the slots can be variously changed.

  FIG. 5 is a diagram illustrating a control channel included in a control region of one subframe in a downlink radio frame.

  Referring to FIG. 5, the subframe is composed of 14 OFDM symbols. Depending on the subframe setting, the first 1 to 3 OFDM symbols are used as a control region, and the remaining 13 to 11 OFDM symbols are used as a data region. In the figure, R1 to R4 represent reference signals (RS) or pilot signals for the antennas 0 to 3. The RS is fixed in a certain pattern within the subframe regardless of the control area and the data area. The control channel is assigned to a resource to which no RS is assigned in the control area, and the information channel is also assigned to a resource to which no RS is assigned in the data area. Control channels allocated to the control area include a physical control format indicator channel (PCFICH), a physical HARQ indicator channel (PHICH), a PDCCH, and the like.

  PCFICH is a physical control format indicator channel, and informs the terminal of the number of OFDM symbols used for PDCCH for each subframe. PCFICH is located in the first OFDM symbol and is set with priority over PHICH and PDCCH. PCFICH is composed of four resource element groups (REG), and each REG is distributed in the control region based on cell identification information (ID). One REG is composed of four resource elements (RE). RE indicates a minimum physical resource defined by one subcarrier × one OFDM symbol. The PCFICH value indicates a value of 1 to 3 or 2 to 4 depending on the bandwidth, and is modulated by quadrature phase shift keying (QPSK).

  PHICH is a physical HARQ indicator channel and is used to carry HARQ ACK / NACK for uplink transmission. That is, PHICH indicates a channel through which DL ACK / NACK information for UL HARQ is transmitted. The PHICH is composed of one REG and is scrambled in a cell-specific manner. ACK / NACK is indicated by 1 bit and is modulated by binary phase shift keying (BPSK). The modulated ACK / NACK is spread with a spreading factor (SF) = 2 or 4. A plurality of PHICHs mapped to the same resource constitute a PHICH group. The number of PHICHs multiplexed in the PHICH group is determined by the number of spreading codes. The PHICH (group) is repeated three times to obtain diversity gain in the frequency domain and / or time domain.

  PDCCH is a physical downlink control channel and is assigned to the first n OFDM symbols of a subframe. Here, n is an integer of 1 or more, and is indicated by PCFICH. The PDCCH is composed of one or more control channel elements (CCE). The PDCCH notifies each terminal or terminal group of information related to resource allocation of PCH and DL-SCH as transmission channels, uplink schedule permission, HARQ information, and the like. The PCH and DL-SCH are transmitted through the PDSCH. Therefore, the base station and the terminal mainly transmit and receive data through the PDSCH, except for specific control information or specific service data.

  PDSCH data is transmitted to which terminal (one or a plurality of terminals), and information on how these terminals should receive and decode PDSCH data is included in the PDCCH and transmitted. . For example, a specific PDCCH is CRC-masked with radio network temporary identification information (RNTI) “A”, radio resource (eg, frequency position) “B”, and transmission format information (eg, transmission block) “C”. It is assumed that information on data transmitted using size, modulation scheme, coding information, etc. is transmitted through a specific subframe. In this case, the terminals in the cell monitor the PDCCH using the RNTI information possessed by the terminal, and if there are one or more terminals having an RNTI of “A”, these terminals use the PDCCH. Receive the PDSCH indicated by “B” and “C” based on the received PDCCH information.

  Hereinafter, a multiple-input multiple-output (MIMO) system will be described. MIMO is a method using a plurality of transmission antennas and a plurality of reception antennas, and this method can improve data transmission / reception efficiency. That is, by using a plurality of antennas at the transmitting end or receiving end in the wireless communication system, the capacity can be increased and the performance can be improved. Hereinafter, MIMO may be referred to as “multiple antennas” in this document.

  In the multi-antenna technology, in order to receive one whole message, data is completed by merging each data fragment received from a plurality of antennas into one without depending on a single antenna path. With multiple antenna technology, it is possible to improve the data transmission rate within a specified size cell area or to increase the system coverage while guaranteeing a specific data transmission rate. In addition, this technology can be widely used for mobile communication terminals and repeaters. According to the multi-antenna technique, it is possible to overcome problems such as a transmission amount limit in the mobile communication according to the conventional technique using a single antenna.

A block diagram of a general multiple antenna (MIMO) communication system is shown in FIG. N _T transmitting antennas are provided at the transmitting end, and N _R receiving antennas are provided at the receiving end. Thus, when a plurality of antennas are used at both the transmitting end and the receiving end, the theoretical channel transmission capacity is compared with the case where a plurality of antennas are used only at either the transmitting end or the receiving end. Will increase. The increase in channel transmission capacity is proportional to the number of antennas. Therefore, transmission speed is improved and frequency efficiency is improved. If the maximum transmission rate in the case of using one antenna is R _o , the transmission rate when using a plurality of antennas is theoretically the maximum transmission rate R _o and the rate of increase R _i as shown in the following equation 1. It can be increased by multiplying by. Here, R _i is a smaller value of N _T and N _R.
(Formula 1)

  For example, in a MIMO communication system using four transmission antennas and four reception antennas, a transmission rate that is theoretically four times higher than that of a single antenna system can be obtained. Since the theoretical capacity increase of such a multi-antenna system was proved in the mid-90s, various techniques for substantially improving the data transmission rate have been actively researched. It has already been reflected in various wireless communication standards such as 3rd generation mobile communication and next generation wireless RAN.

  Looking at multi-antenna related research trends to date, research on information theory related to multi-antenna communication capacity calculation in various channel environments and multiple access environments, research on radio channel measurement and model derivation of multi-antenna systems, and Active research has been conducted from various viewpoints such as space-time signal processing technology research for improving transmission reliability and transmission rate.

When this is mathematically modeled to more specifically describe the communication method in a multiple antenna system, it can be shown as follows. As shown in FIG. 6, it is assumed that there are N _T transmit antennas and N _R receive antennas. First, regarding a transmission signal, when there are N _T transmission antennas, the maximum transmittable information is N _T , so that the transmission information can be represented by a vector as shown in Equation 2 below.
(Formula 2)

On the other hand, each of the transmission information _{S 1,} S 2, _..., it is possible to vary the transmission power in _{S NT,} this time, the respective transmit power _{P 1,} P 2, _..., if _{P NT,} transmit power When the adjusted transmission information is expressed as a vector, it is as shown in Equation 3 below.
(Formula 3)

（式４）

(Formula 4)

On the other hand, considering the case is applied adjusted information vector hat-S in weight matrix W of the transmitted power is actually transmitted the N _T transmitted signals _{x 1, x 2, ...,} x NT is configured Try. Here, the weight matrix plays a role of appropriately distributing transmission information to each antenna according to a transmission channel condition or the like. Such transmission signals x ₁ , x ₂ ,..., X _NT can be expressed as the following Expression 5 using a vector x. Here, W _ij means a weight value between the i-th transmitting antenna and the j-th information. W is called a weight matrix or a precoding matrix.
(Formula 5)

In general, the physical meaning of the rank of the channel matrix can be said to be the maximum number of distinct information that can be sent on a given channel. Accordingly, since the rank of the channel matrix is defined as the minimum number of rows or columns that are independent from each other, the rank of the matrix is never greater than the number of rows or columns. For example, the rank rank (H) of the channel matrix H is limited as shown in Equation 6.
(Formula 6)

Also, each piece of separate information sent using the multi-antenna technology is defined as “transmission stream” or simply “stream”. Such a “stream” can also be called a “hierarchy”. Therefore, as a matter of course, the number of transmission streams does not exceed the rank of the channel, which is the maximum number that can transmit separate information. Therefore, the channel matrix H can be expressed as in Equation 7 below.
(Formula 7)

  Here, “# of streams” represents the number of streams. However, it should be noted here that one stream may be transmitted through one or more antennas.

  There are various methods for associating one or more streams with a plurality of antennas. These methods can be distinguished as follows according to the type of multi-antenna technology. When one stream is transmitted via a plurality of antennas, a spatial diversity scheme can be used, and when a plurality of streams are transmitted via a plurality of antennas, a spatial multiplexing scheme can be employed. Of course, a mixed form (Hybrid) of spatial diversity and spatial multiplexing is also possible.

  Hereinafter, the reference signal will be described in more detail. In general, for channel measurement, a reference signal that is already known by both the transmission side and the reception side is transmitted from the transmission side to the reception side together with the data. Such a reference signal is demodulated by informing the modulation method in addition to the channel measurement. The reference signal includes a dedicated reference signal (DRS) for the base station and the specific terminal, that is, a terminal specific reference signal and a common reference signal (CRS) that is a cell specific reference signal for all terminals in the cell. being classified. The cell specific reference signal includes a reference signal for measuring CQI / PMI / RI at the terminal and reporting it to the base station, and this is referred to as a channel state information reference signal (CSI-RS).

  FIG. 7 is a diagram illustrating the structure of a reference signal in an LTE system that supports downlink transmission using four antennas. In particular, FIG. 7a shows the case of a normal cyclic prefix, and FIG. 7b shows the case of an extended cyclic prefix.

  Referring to FIG. 7, 0 to 3 described in the lattice mean CRS that is a cell specific reference signal transmitted for channel measurement and data demodulation corresponding to each of the antenna ports 0 to 3. The CRS that is the cell specific reference signal can be transmitted to the terminal over the entire control information area in addition to the data information area.

  Also, 'D' described in the lattice means a downlink DM-RS that is a terminal specific RS, and the DM-RS supports single antenna port transmission through a data region, that is, PDSCH. The terminal is notified from the upper layer whether or not the DM-RS which is the terminal specific RS exists.

（式９）

（式１０）

On the other hand, the mapping rule of the reference signal to the resource block (RB) can be expressed by the following Expression 8 to Expression 10. Equation 8 below shows the CRS map rule, Equation 9 shows the DRS map rule to which the general CP is applied, and Equation 10 shows the DRS map rule to which the extended CP is applied.
(Formula 8)

(Formula 9)

(Formula 10)

In Equations 8 to 10, k and p represent a subcarrier index and an antenna port, respectively. N ^DL _RB , ns, and N ^ID _cell represent the number of RBs assigned to the downlink, the number of slot indexes, and the number of cell IDs, respectively. The position of the RS varies depending on the V _shift value in terms of the frequency domain.

  Hereinafter, a transmission mode (TM) for transmitting the PDSCH will be described based on the current LTE standard document.

  FIG. 8 is a diagram illustrating a relationship between a transmission mode for transmitting the PDSCH and a DCI format indicated by the PDCCH. As described above, information on how the terminal should receive and decode the PDSCH data is included in the PDCCH and transmitted. Therefore, the PDCCH is CRC-masked with an RNTI “A”, and can include information on a DCI format for receiving the PDSCH.

  Referring to FIG. 8, a DCI format according to the type of RNTI masking PDCCH is shown. In particular, in the case of C-RNTI and SPSC-RNTI, a transmission mode and a corresponding DCI format, ie, a transmission mode based The DCI format is shown. In addition, a DCI format 1A that can be applied regardless of each transmission mode is defined.

  In particular, the DCI format 1A is a fall for scheduling of one PDSCH codeword to enable stable signal transmission / reception when the transmission mode is changed or during the RRC connection reconfiguration process between the base station and the terminal. It is a DCI format for back mode. For example, during the reconfiguration process between the base station and the terminal, the base station can transmit the PDSCH as the DCI format 1A when the time points at which the reconfigured parameters are applied do not match.

  More specifically, according to the current standard document, when DCI format 1A is detected from the PDCCH masked with C-RNTI, regardless of the set transmission mode, the PDCCH is detected as a CRS of a single antenna port. , The PDSCH is decoded assuming single antenna transmission of the antenna port 0. In other cases, the PDSCH is decoded assuming that the PDSCH is transmitted by the transmission diversity method.

  On the other hand, the LTE-A system, which is a standard for next-generation mobile communication systems, is expected to support a multi-point coordinated transmission / reception (CoMP) system that is not supported by the existing standard in order to improve the data transmission rate. Here, the CoMP system is a system in which two or more base stations or cells communicate with a terminal in cooperation with each other in order to improve communication performance between the terminal and the base station (cell or sector) in the shaded area. Say.

  The CoMP scheme can be distinguished into a cooperative MIMO form joint processing (CoMP-JP) scheme using data sharing and a cooperative schedule / beamforming (CoMP-CS / CB) scheme.

  In the case of the downlink, in the joint processing (CoMP-JP) scheme, the terminal can receive data from each base station that performs CoMP instantaneously and simultaneously, and the received signals from the base stations are combined and received. Performance can be improved. In contrast, in the coordinated schedule / beamforming scheme (CoMP-CS), a terminal can instantaneously receive data from one base station through beamforming.

  In the case of uplink, in the joint processing (CoMP-JP) scheme, each base station can simultaneously receive a PUSCH signal from a terminal. In contrast, in the coordinated schedule / beamforming scheme (CoMP-CS), only one base station receives the PUSCH. At this time, the decision to use the coordinated schedule / beamforming scheme is the coordinated cell (or base station). Each other decides.

  On the other hand, when the channel state between the base station and the terminal is not good, it is possible to provide a wireless channel with a better channel state to the terminal by providing a relay node (RN) between the base station and the terminal. . In addition, by introducing and using a relay node from a base station in a cell boundary area where the channel state is not good, it is possible to provide a higher-speed data channel and expand the cell service area. As described above, the relay node is a technique introduced for eliminating a radio wave shadow area in a wireless communication system, and is currently widely used.

  While the past schemes have remained as repeater functions that simply amplify and transmit signals, recent ones have evolved into more intelligent forms. Note that the relay node technology is an indispensable technology for expanding the service coverage and improving the data processing rate as well as reducing the base station extension cost and the backhaul network maintenance cost in the next generation mobile communication system. As relay node technology develops, it is necessary for new wireless communication systems to support relay nodes used in conventional wireless communication systems.

  In the 3GPP LTE-A system, by introducing a function of transferring a link connection between a base station and a terminal to a relay node, two types of links having different attributes are provided in each uplink and downlink carrier frequency band. Will be applied. A connection link portion set between the link between the base station and the relay node is defined as a backhaul link. The transmission using the FDD or TDD scheme using the downlink resource is expressed as a backhaul downlink, and the transmission using the FDD or TDD scheme using the uplink resource is expressed as a backhaul uplink. can do.

  FIG. 9 is a diagram illustrating a configuration of the relay backhaul link and the relay access link in the wireless communication system.

  Referring to FIG. 9, a relay node is introduced as a function for forwarding a link connection between a base station and a terminal, and thus an attribute is assigned to each uplink and downlink carrier frequency band. Two different types of links are applied. A connection link portion set between the base station and the relay node is defined as a relay backhaul link. When the backhaul link is transmitted by a downlink frequency band (in case of FDD) or downlink subframe (in case of TDD) resource, it is expressed as a backhaul downlink and uplink frequency band (in case of FDD). Alternatively, when transmission is performed using an uplink subframe (in case of TDD) resource, it can be expressed as a backhaul uplink.

  On the other hand, a connection link portion set between a relay node and a series of terminals is defined as a relay access link. When a relay access link is transmitted by a downlink frequency band (in the case of FDD) or downlink subframe (in the case of TDD) resource, it is expressed as an access downlink, and the uplink frequency band (in the case of FDD) or up When transmission is performed by a link subframe (in the case of TDD) resource, it can be expressed as an access uplink.

  The relay node (RN) can receive information from the base station through the relay backhaul downlink and transmit information to the base station through the relay backhaul uplink. Also, the relay node can transmit information to the terminal through the relay access downlink and receive information from the terminal through the relay access uplink.

  On the other hand, regarding the use of the band (or spectrum) of the relay node, the case where the backhaul link operates in the same frequency band as the access link is called “in-band”, and the backhaul link and the access link are different. The case of operating in the frequency band is referred to as “out-band”. In both in-band and out-of-band, a terminal operating in accordance with an existing LTE system (for example, Release-8) (hereinafter referred to as a legacy terminal) must be able to connect to the donor cell.

  Depending on whether the terminal recognizes the relay node, the relay node can be classified into a transparent relay node and a non-transparent relay node. Transparent refers to the case where the terminal cannot recognize whether to communicate with the network through the relay node, and non-transparent refers to the case where the terminal recognizes whether to communicate with the network through the relay node.

  Regarding the control of the relay node, the relay node can be classified into a relay node configured as a part of the donor cell and a relay node that controls the cell by itself.

  A relay node configured as part of a donor cell can have a relay node identifier (ID), but does not have its own cell identification information (identity). When at least a part of radio resource management (RRM) is controlled by the base station to which the donor cell belongs (even if the rest of the RRM is located in the relay node), it is defined as a relay node configured as part of the donor cell . Preferably, such a relay node can support older terminals, eg various types of smart repeaters, decode-and-forward relays, layer 2 (L2) relay nodes And corresponds to a type 2 relay node.

  The relay node that controls the cell itself controls one or a plurality of cells, each of the cells controlled by the relay node is provided with unique physical layer cell identification information, and the same RRM mechanism can be used. For the terminal, there is no difference between accessing a cell controlled by a relay node and accessing a cell controlled by a general base station. Preferably, cells controlled by such relay nodes can support older terminals. This relay node corresponds to, for example, a self-backhauling relay node, a third layer (L3) relay node, a type 1 relay node, and a type 1a relay node.

  A type 1 relay node is an in-band relay node that controls a plurality of cells, each of which is considered a separate cell for the terminal to be distinguished from a donor cell. The plurality of cells have unique physical cell IDs (defined in LTE Release-8), and the relay node can transmit its own synchronization channel, reference signal, and the like. In case of single cell operation, the terminal can receive the schedule information and HARQ feedback directly from the relay node, and can transmit its control channel (schedule request (SR), CQI, ACK / NACK, etc.) to the relay node. . Also, for older terminals (terminals operating according to the LTE Release-8 system), type 1 relay nodes are considered as older base stations (base stations operating according to the LTE Release-8 system). That is, it has backward compatibility. On the other hand, for terminals operating in accordance with the LTE-A system, the type 1 relay node is regarded as a base station different from the old base station, and can provide improved performance.

  Type 1a relay nodes have the same characteristics as the type 1 relay nodes described above, except that they operate out of band. The operation of the type 1a relay node can be configured so that the impact on the first layer (L1) operation is minimized or not.

  A type 2 relay node is an in-band relay node and does not have a separate physical cell ID and therefore does not form a new cell. The type 2 relay node is transparent to the old terminal, and the old terminal cannot recognize the presence of the type 2 relay node. Type 2 relay nodes can transmit PDSCH, but do not transmit at least CRS and PDCCH.

  On the other hand, in order for the relay node to operate in band, some resources in the time-frequency space must be reserved for the backhaul link, and this resource is used for the access link. Can be set to not. This is called resource division.

  The general principle of resource division in a relay node is as follows. The backhaul downlink and the access downlink can be multiplexed in a time division multiplexing (TDM) manner on one carrier frequency (ie, only one of the backhaul downlink or the access downlink at a specific time) Activate). Similarly, the backhaul uplink and access uplink can be multiplexed in a TDM manner on one carrier frequency (ie, only one of the backhaul uplink or access uplink is activated at a specific time) To do).

  Backhaul link multiplexing in FDD can be described as backhaul downlink transmission is performed in the downlink frequency band and backhaul uplink transmission is performed in the uplink frequency band. In the backhaul link multiplexing in TDD, the backhaul downlink transmission is performed in the downlink subframe between the base station and the relay node, and the backhaul uplink transmission is performed in the uplink subframe between the base station and the relay node. It can be explained as a thing.

  In the case of an in-band relay node, for example, when backhaul downlink reception from a base station and access downlink transmission to a terminal are simultaneously performed in a predetermined frequency band, a signal transmitted from the transmission end of the relay node May be received at the receiving end of the relay node, which may cause signal interference or RF jamming at the RF front end of the relay node. Similarly, if reception of an access uplink from a terminal and transmission of a backhaul uplink to a base station are simultaneously performed in a predetermined frequency band, signal interference may occur in the RF front end of the relay node. Therefore, in order to enable simultaneous transmission and reception in one frequency band in the relay node, sufficient separation between the reception signal and the transmission signal (for example, the transmission antenna and the reception antenna are sufficiently separated geographically). (E.g., set up above ground / underground).

  One proposal for solving such a problem of signal interference is that the relay node is configured not to transmit a signal to the terminal while receiving a signal from the donor cell. That is, it is possible to set a gap in transmission from the relay node to the terminal so that the terminal (including the old terminal) does not expect any transmission from the relay node. This gap can be set by configuring a multicast broadcast single frequency network (MBSFN) subframe.

  FIG. 10 is a diagram illustrating an example of relay node resource division.

  In FIG. 10, the first subframe is a general subframe, a downlink (ie, access downlink) control signal and data are transmitted from the relay node to the terminal, and the second subframe is an MBSFN subframe, In the control region of the downlink subframe, a control signal is transmitted from the relay node to the terminal, but in the remaining region of the downlink subframe, no transmission is performed from the relay node to the terminal. Here, in the case of an old-type terminal, transmission of a physical downlink control channel (PDCCH) is expected in all downlink subframes (in other words, a relay node is connected to an old-type terminal in its own region. Therefore, it is necessary to transmit the PDCCH in all downlink subframes for correct operation of the old terminal. Therefore, even in the subframe (second subframe 1020) set for downlink (ie, backhaul downlink) transmission from the base station to the relay node, the top N (N = 1, 2) of the subframe is set. Or 3) In the OFDM symbol period, the relay node does not receive the backhaul downlink and needs to perform access downlink transmission. In this regard, since the PDCCH is transmitted from the relay node to the terminal in the control region of the second subframe, it is possible to provide backward compatibility with the old terminal serviced by the relay node. In the remaining area of the second subframe, the relay node can receive the transmission from the base station while no transmission is performed from the relay node to the terminal. Such resource partitioning scheme can prevent simultaneous access downlink transmission and backhaul downlink reception at the in-band relay node.

The second subframe using the MBSFN subframe will be specifically described. The control area of the second subframe may be referred to as a relay node non-hearing period. The relay node non-listening period refers to a period in which the relay node transmits an access downlink signal without receiving a backhaul downlink signal. This section can be set to 1, 2, or 3 OFDM lengths as described above. In the relay node non-listening period, the relay node performs access downlink transmission to the terminal, and can receive the backhaul downlink from the base station in the remaining area. In this case, since the relay node cannot simultaneously transmit and receive in the same frequency band, it takes time for the relay node to switch from the transmission mode to the reception mode. Therefore, it is necessary to set the protection time (GT) so that the relay node performs transmission / reception mode switching in the first partial section of the backhaul downlink reception area. Similarly, when the relay node receives the backhaul downlink from the base station and operates to transmit the access downlink to the terminal, the protection time for switching the reception / transmission mode of the relay node is set. can do. The length of such guard time can be given as a value in the time domain, for example, it can be given as k (k ≧ 1) time sample (T _s ) values, or one or more OFDM symbols. It may be set to long. Or, when relay node backhaul downlink subframes are set continuously, or according to a predetermined subframe timing alignment relationship, the guard time of the last part of the subframe may not be defined or set. . Such a guard time can be defined only in the frequency domain set for backhaul downlink subframe transmission to maintain backward compatibility (the guard time is set in the access downlink zone). Cannot support older terminals). In the backhaul downlink reception period other than the protection time, the relay node can receive PDCCH and PDSCH from the base station. This can also be expressed as a relay node PDCCH (R-PDCCH) and a relay node PDSCH (R-PDSCH) in the sense of a relay node specific physical channel.

  On the other hand, the R-PDSCH can be demodulated based on two types of reference signals, that is, CRS or DM-RS. However, when an MBSFN subframe is used when the base station transmits a downlink signal to the relay base station, there is no CRS for demodulating the PDSCH transmitted by the transmission diversity method in the MBSFN subframe. Therefore, it is preferable that the relay base station demodulates the R-PDSCH using DM-RS that can be transmitted in all types of subframes.

  Also, if the DCI format detected as a result of decoding the R-PDCCH is the DCI format 1A applied to the fallback mode, a field in which the base station can inform the relay node of rank information is included in the DCI format 1A. Does not exist. Therefore, when the DCI format 1A is detected as a result of decoding the R-PDCCH, particularly the downlink grant transmitted in the first slot in one subframe, the relay node can be transmitted in the second slot. I don't know the actual transmission rank of R-PDSCH.

  In the present invention, when the relay node detects DCI format 1A as a result of decoding the R-PDCCH, the R-PDSCH transmission corresponding to the R-PDCCH is the most reliable single antenna port transmission. We propose to assume That is, the relay node proposes to demodulate and decode the R-PDSCH under the assumption that the base station is transmitting R-PDSCH in rank 1. The details are as follows.

  FIG. 11 shows a case where 12 resource elements for DM-RS are allocated in one resource block pair, and FIG. 12 shows that 24 resource elements for DM-RS are allocated in one resource block pair. Indicates the case where

  The number of DMRS resource elements required varies according to the actual transmission rank of the R-PDSCH. However, in the case of rank 1 or 2, as shown in FIG. 11, one resource block pair across the first slot and the second slot is used. In FIG. 12, when 12 resource elements have a rank of 3 or higher, 24 resource elements are required in one resource block pair as shown in FIG. Therefore, in order to decode the R-PDSCH in a state where the relay node does not know the actual transmission rank, the relay node needs to assume the number of DMRS resource elements for demodulating and decoding the R-PDSCH.

  In this case, according to the present invention, if the DCI format 1A indicating the fallback mode is detected as a transmission format for the R-PDSCH as a result of blind decoding of the R-PDCCH, the R-PDSCH is a single antenna. Since demodulation and modulation are performed on the assumption that the transmission port is always transmitted in rank 1, 12 resource elements are allocated as resource elements for DM-RS at the time of R-PDSCH decoding as shown in FIG. It is preferable to set that.

  For example, even if the relay node is notified of two or four antenna ports as antenna ports for DM-RS by an upper layer signal, the relay node that detects DCI format 1A always ranks R-PDSCH. 1 and the R-PDSCH can be demodulated and decoded under the assumption that the DM-RS is assigned to 12 resource elements.

  Further, in the present invention, when the base station transmits to the relay node a DM-RS that is a base station specific reference signal, that is, when a DM-RS-based R-PDCCH is transmitted, the relay node transmits the R-PDCCH. If the DCI format 1A applied to the fallback mode is detected as a transmission format of R-PDSCH, it is proposed to decode data, that is, R-PDSCH using a preset logical antenna port. . Here, the logical antenna port is defined by an antenna port and a scramble ID.

  Specifically, the R-PDCCH can be configured to demodulate and decode the R-PDSCH using the logical antenna port of the DM-RS used for R-PDCCH demodulation, that is, the antenna port and the scramble ID. The DM-RS logical antenna port used for demodulation is preferably 7 (or 8) antenna port and 0 (or 1) scramble ID. If the R-PDCCH is successfully demodulated and decoded using DM-RS, the logical antenna port used for demodulating the R-PDCCH can maintain good communication with the corresponding relay node. This is because there is a high possibility that the beam is formed.

  Therefore, if the relay node decodes the DM-RS based R-PDCCH and detects DCI format 1A, it assumes the single antenna port transmission and decodes the R-PDSCH. In this case, the R-PDSCH Is preferably demodulated and decoded using the logical antenna port of the DM-RS used at the time of R-PDCCH demodulation, for example, antenna port 7 (or 8) and scramble ID 0 (or 1).

  FIG. 13 is a block diagram of a communication apparatus according to an embodiment of the present invention.

  Referring to FIG. 13, the communication apparatus 1300 includes a processor 1310, a memory 1320, an RF module 1330, a display module 1340, and a user interface module 1350.

  The communication device 1300 is illustrated for convenience of explanation, and some modules may be omitted. Note that the communication device 1300 may further include a necessary module. In addition, some modules in the communication device 1300 may be subdivided modules. The processor 1310 is configured to perform the operations according to the embodiment of the present invention exemplified with reference to the drawings. Specifically, for the detailed operation of the processor 1310, refer to the contents described in FIGS.

  The memory 1320 is connected to the processor 1310 and stores an operating system, applications, program codes, data, and the like. The RF module 1330 is connected to the processor 1310 and performs a function of converting a baseband signal into a radio signal and converting a radio signal into a baseband signal. For this, the RF module 1330 performs analog conversion, amplification, filtering and frequency up-conversion, or the reverse process. The display module 1340 is connected to the processor 1310 and displays various information. The display module 1340 may use well-known elements such as, but not limited to, a liquid crystal display (LCD), a light emitting diode (LED), and an organic light emitting diode (OLED). The user interface module 1350 connects to the processor 1310 and can be configured with a combination of well-known user interfaces such as a keypad, touch screen, and the like.

  In the embodiment described above, the constituent elements and features of the present invention are combined in a predetermined form. Each component or feature should be considered optional unless stated otherwise. Each component or feature may be implemented in a form that is not combined with other components or features, or some components and / or features may be combined to form an embodiment of the present invention. The order of operations described in the embodiments of the present invention can be changed. Some configurations or features of one embodiment may be included in another embodiment, and may be replaced with corresponding configurations or features of another embodiment. It is obvious that claims which do not have an explicit citation relationship in the claims can be combined to constitute an embodiment, or can be included as a new claim by amendment after application.

  In the present specification, the embodiments of the present invention have been described mainly on the data transmission / reception relationship between the relay node and the base station. The specific operation assumed to be performed by the base station in this specification may be performed by the higher order node in some cases. That is, it is apparent that various operations performed for communication with a terminal in a network including a large number of network nodes including a base station may be performed by the base station or another network node other than the base station. The base station can be replaced with terms such as a fixed station, a Node B, an evolved Node B (eNB), and an access point.

  Embodiments according to the present invention can be implemented by various means, for example, hardware, firmware, software, or a combination thereof.

  When implemented in hardware, one embodiment of the invention includes one or more application specific integrated circuits (ASICs), digital signal processors (DSPs), digital signal processing devices (DSPDs), programmable logic devices (PLDs). ), A field programmable gate array (FPGA), a processor, a controller, a microcontroller, a microprocessor, and the like.

  In the case of implementation by firmware or software, an embodiment of the present invention may be implemented in the form of a module, procedure, function, or the like that performs the functions or operations described above. The software code may be stored in a memory unit and driven by a processor. The memory unit is provided inside or outside the processor, and can exchange data with the processor by various known means.

  It will be apparent to those skilled in the art that the present invention can be embodied in other specific forms without departing from the features of the present invention. As such, the above detailed description should not be construed as limiting in any respect, but should be considered exemplary. The scope of the present invention should be determined by reasonable interpretation of the appended claims, and all modifications within the equivalent scope of the present invention are included in the scope of the present invention.

  In the wireless communication system as described above, the method for determining the size of the transmission block transmitted from the base station to the relay node and the apparatus therefor have been described mainly with reference to an example applied to the 3GPP LTE system. The present invention can also be applied to various multi-antenna wireless communication systems.

Claims (14)

A method for receiving a relay node specific downlink physical shared channel (R-PDSCH) from a base station in a relay node of a multi-antenna wireless communication system, comprising:
Demodulating a relay node specific downlink physical control channel (R-PDCCH) using a relay node specific reference signal;
When specific downlink control information is detected from the demodulated relay node specific downlink physical control channel, the relay node specific downlink physical shared channel is transmitted through a single antenna port using a predetermined antenna port and a scramble identifier. Demodulating the relay node specific downlink physical shared channel under the assumption that it was transmitted;
Having a method.   The method of claim 1, wherein the relay node specific reference signal corresponds to a demodulation reference signal (DM-RS).   The method of claim 1, wherein the specific downlink control information corresponds to downlink control information indicating a fallback mode.   The method of claim 1, wherein the downlink control information indicating the fallback mode corresponds to a downlink control information (DCI) format 1A.   The method according to claim 1, wherein the predetermined antenna port and scramble identifier correspond to the antenna port and scramble identifier of the relay node specific reference signal used when demodulating the relay node specific downlink physical control channel, respectively.   The method of claim 1, wherein the predetermined antenna port and scramble identifier correspond to antenna port 7 and scramble identifier 0, respectively.   The method of claim 1, wherein the relay node specific downlink physical control channel and the relay node specific downlink physical shared channel are transmitted over a multicast broadcast single frequency network (MBSFN) subframe. A relay node in a multi-antenna wireless communication system,
A receiving module configured to receive a relay node specific downlink physical control channel (R-PDCCH) and a relay node specific downlink physical shared channel (R-PDSCH) from the base station;
The relay node specific downlink physical control channel is demodulated based on the relay node specific reference signal, and the relay node specific downlink is determined based on the specific downlink control information detected from the demodulated relay node specific downlink physical control channel. A processor configured to decode the link physical shared channel;
The processor demodulates the relay node specific downlink physical shared channel under the assumption that the relay node specific downlink physical shared channel is transmitted through a single antenna port using a predetermined antenna port and a scramble identifier. Relay node.   The relay node according to claim 8, wherein the relay node specific reference signal corresponds to a demodulation reference signal (DM-RS).   The relay node according to claim 8, wherein the specific downlink control information corresponds to downlink control information indicating a fallback mode.   The relay node according to claim 10, wherein the downlink control information indicating the fallback mode corresponds to a downlink control information (DCI) format 1A.   The relay node according to claim 8, wherein the predetermined antenna port and scramble identifier correspond to the antenna port and scramble identifier of the relay node specific reference signal used when demodulating the relay node specific downlink physical control channel, respectively.   The relay node according to claim 8, wherein the predetermined antenna port and scramble identifier correspond to the antenna port 7 and scramble identifier 0, respectively.   The relay node according to claim 8, wherein the receiving module receives the relay node specific downlink physical control channel and the relay node specific downlink physical shared channel through a multicast broadcast single frequency network (MBSFN) subframe.

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